They are not unix-style paths. They are paths with "/" separators. This is
not Windows vs Unix. Hell, just stop thinking about them as *paths*.
Consider them to be "locators" or something. Separate the segments and use
the array of segments to skip down into subdirs to find your file.

Who says they have to be *filesystem* paths? Who said these are being pass
to the operating system?

You need to convert your local filesystem paths into Subversion's model. We
provide functions for it. Within the Subversion libraries, and at its edge
points (the API), everything operates within Subversion's model.